INFLUENCE OF THE γ↔α TRANSFORMATION ON HIGH-TEMPERATURE DUCTILITY OF MICRO-ALLOYED PIPE STEELS

We have investigated the ductility of micro-alloyed pipe steels in the temperature range of γ↔α transformations for physical modeling of continuous casting and hot rolling conditions. Physical simulation was performed on the thermomechanical Gleeble-3800 complex. It was found that the decline in the ductility of steel studied in a two-phase region in the simulation of continuous casting of steel due to the conditions of allocation of ferrite grain boundaries of austenite to form a thin layer on the boundaries. This causes strain localization and premature failure of the metal. It is shown that the formation of cracks at the interfaces during a simulation of austenite-ferrite hot rolling in a two phase region does not occur and the steel has high ductility. However, the study of limiting stresses (tensile strength) that could cause the destruction of the metal has shown that these stresses have a complex temperature dependence, and are structurally dependent, their size determined by the type of the transformation (ferrite and bainite) in the steel. The nature of bainite transformation determines the rise and fall of tensile strength.